package com.lession.util;


import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * MD5加密工具类
 */
public class MD5Utils {
	
	// 全局数组
	private final static String[] strDigits = {
			"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F"
	};
	
	private static String byteToArrayString(byte bByte) {
		int iRet = bByte;
		// System.out.println("iRet="+iRet);
		if (iRet < 0) {
			iRet += 256;
		}
		int iD1 = iRet / 16;
		int iD2 = iRet % 16;
		return strDigits[iD1] + strDigits[iD2];
	}
	
	// 返回形式只为数字
	private static String byteToNum(byte bByte) {
		int iRet = bByte;
		//System.out.println("iRet1=" + iRet);
		if (iRet < 0) {
			iRet += 256;
		}
		return String.valueOf(iRet);
	}
	
	// 转换字节数组为16进制字串
	private static String byteToString(byte[] bByte) {
		StringBuffer sBuffer = new StringBuffer();
		for (int i = 0; i < bByte.length; i++) {
			sBuffer.append(byteToArrayString(bByte[i]));
		}
		return sBuffer.toString();
	}
	
	/**
	 * 加密
	 */
	public static String getMD5Code(String strObj) {
		String resultString = null;
		try {
			resultString = new String(strObj);
			MessageDigest md = MessageDigest.getInstance("MD5");
			// md.digest() 该函数返回值为存放哈希值结果的byte数组
			resultString = byteToString(md.digest(strObj.getBytes()));
		} catch (NoSuchAlgorithmException ex) {
			ex.printStackTrace();
		}
		return resultString;
	}
	
	
	/**
	 * 32位小写
	 *
	 * @param strObj
	 * @return
	 */
	public static String getMD5CodeLower(String strObj) {
		String resultString = null;
		try {
			MessageDigest md = MessageDigest.getInstance("MD5");
			byte[] messageDigest = md.digest(strObj.getBytes());
			StringBuilder hexString = new StringBuilder();
			for (byte b : messageDigest) {
				String hex = Integer.toHexString(0xFF & b);
				if (hex.length() == 1) {
					hexString.append('0');
				}
				hexString.append(hex);
			}
			resultString = hexString.toString();
		} catch (NoSuchAlgorithmException ex) {
			ex.printStackTrace();
		}
		return resultString;
	}
	
	
}
